Nano-energetic materials are mixtures of fuel and oxidizers closely packed together for a self-sustaining, high temperature reaction. Tiny particles have increased surface area over larger particles. Close proximity of the fuel and the oxidizer create waves of energy as the flame propagates through the solid material. Energy from adjacent layers ignites the fuel/oxidizer mixture. Material can be used as prepared or modified with polymers or explosives and used as a primers for explosives or propellants. Materials of this type have potential application in mining, demolitions, precision cutting, explosive welding, surface treatment and hardening of materials, pulse owner, crystallization and solar cells, sintering, micro-aerospace, satellite platforms, military applications and biomedical fields that destroy localized pathological tissues. Other prominent applications include thermite torches for underwater and atmospheric cutting or perforation, electronic hardware devices, additives to propellants and explosives having increased performance, pyrotechnic switches, airbag gas generator materials, high-temperature stable igniters, freestanding insertable heat sources, devices to breach ordnance cases to relieve pressure during fuel fires, thermal battery heat sources, incendiary projectiles, delay fuses, additives to propellants to increase burn rate without decrease of specific impulse and full sized shape-charged liners.
There are a few types of on-chip ignition devices such as exploding bridge-wires (“EBW”) and exploding foil initiators (“EFI”). The EBW and EFI devices are electro-shock initiated devices. These types of devices have fast and repeatable function times. They also have a high resistance to accidental initiation. However, EBW devices, such as the tungsten bridge, when supplied with current, causes plasma to form which vaporizes the tungsten and causes the ignition of the energetic material. EBWs also take the form of a semiconductor bridge, which operates in a similar manner. It produces plasma when current flows which then vaporizes the bridge material. These devices are fabricated on silicon, sapphire, or silicon-on-sapphire substrates. They are capable of initiation with energies below 100 mJ.
A common method for the ignition of nano-thermites is by laser heating. With laser powers of 50 W, or 100 W/cm2 such thermites have been ignited in 21 ms. Such setups are very large and expensive.
There are many types of thin-film resistive heaters in use at the present time. Thin-film platinum heaters are used where surface heating is necessary. They have been used for crystallization of ceramic films, and for sensor reactivation. They have also been used to melt solder for the attachment of optoelectronic components to substrates.
There is a need for low power and low cost ignitors (initiators) for many applications mentioned above. These ignitors should be inexpensive and convenient and easy and safe to handle. They can be fabricated for controlling the ignition delay and tailor the properties of energetic material and heater for specific applications.
As the materials to be detonated become more sophisticated, the flame propagation speed and the propagation of the flame front become faster, and materials to test them must adapt accordingly. For the applications cited above, it is important to have a thorough knowledge of the ignition characteristics of nanoenergetics materials. Available methods for testing are also expensive. Some test methods require high-end digital imaging systems. Testing devices that are unable to distinguish new products from each other are useless for screening new products. Large-scale testing systems are not always available for investigation or rare, expensive or highly toxic statistical analysis or small labs on limited budgets.
Several diagnostic methods are used to study ignition characteristics of nanoenergetic materials. Some of these mechanisms include shock loading, electric exploding foil accelerators, light-ion-beam driver for flyer plate acceleration and indirect irradiation of the target material with a high-intensity pulsed laser. Some of the prior art literature mentions multi-metal foils, typically aluminum or nickel. The flame velocity is then measured by sputtering metal bilayer on a polished silicon substrate and then separating the film from the surface and taping the free standing bimetallic multilayered foil (obtained by cleaving the silicon substrate and carefully peeling off) over another substrate for structural stability.
These methods are very expensive and some require installation of high-speed digital imaging systems. Initiation of the reaction is by localized heating and detection of flame using an array of optical fibers. This method requires an oscilloscope or other expensive optical set up. Each of these methods offers advantages but also significant limitations. The direct laser technique requires extensive tailoring of the laser temporal and spatial profile to avoid the production of ill-conditioned shock waves. The light-ion-beam and radiation drivers generally do not permit rapid turn around. Other characterization techniques use expensive high-speed movie cameras. Moreover, these large-scale systems are impractical for investigation of rare, expensive or highly toxic materials.